This invention relates generally to the field of systems configured to simulate aerodynamic pressure loadings on airfoils, and more particularly to a novel bellows array structure configured to simulate the aerodyhnamic loading.
The present invention provides a new and improved method and apparatus for simulating aerodynamic load distributions over the surface of an airfoil, such as an airplane wing or the like, and is useful for the structural testing of aircraft. Simulation of inertial loadings experienced by the airfoil may also be easily accommodated. The apparatus of the present invention comprises a matrix array of bellows-type pressure cells in contact with the airfoil surfaces. The internal pressures (positive pressure or partial vacuum) of each cell may be individually computer controlled through a Scani valve sensing arrangement to provide the desired simulated aerodynamic load distributions over substantially the entire airfoil surface area. The bellows matrix arrangement may be sized and configured to conform to substantially any surface contour to be tested.
The simulated aerodynamic loading apparatus of the present invention enjoys certain significant advantages over previously known devices. In particular, the novel apparatus herein described can be configured to include a variable loading support structure in order to follow large airfoil deflections, or the bellows matrix arrangement may be supported by a fixed structure for simulation testing involving small deflections of the airfoil. The stabilization network providing lateral support to each of the plurality of bellows in the matrix array allows conformance of the apparatus to airfoil surface contours and, in addition, provides the necessary lateral stability to each bellows under pressure. The invention herein is therefore particularly useful in testing variable surface contour airfoil designs. Testing inaccuracies due to approximations characteristically made in the use of certain previously known systems utilizing tension pads or point loading are substantially eliminated through the use of the apparatus described herein. Further, the apparatus of this invention is characterized by relative ease and speed with which it can be assembled for a testing program and subsequently disassembled at program end, as compared to existing systems. The "tension patch" system currently conventionally used can create undesirable localized skin stresses which may be unacceptable in the testing of modern, thin skinned, bonded and composite surfaces. The present invention substantially eliminates or reduces in critical importance the foregoing problems with existing systems.
It is, therefore, an object of the present invention to provide an improved system for simulating the aerodynamic loading distribution on an airfoil.
It is a further object of the present invention to provide an aerodynamic load simulation apparatus conformable to substantially any airfoil surface contour.
It is yet another object of the present invention to provide an improved method for testing airfoil structures under conditions of simulated aerodynamic loading.
These and other objects of the present invention will become apparent as the detailed description of representative embodiments thereof proceeds.